Cellulosic fibers are multi-component structures made from cellulose polymers, i.e. cellulose chains. Lignin, pentosans and other components known in art may also be present. The cellulose chains in the fibers are attached to each other to form elementary fibrils. Several elementary fibrils are bound to each other to form microfibrils and several microfibrils form aggregates. The links between the cellulose chains, elementary- and microfibrils are hydrogen bonds.
Microfibrillated cellulose (MFC) (also known as nanocellulose) is a material made from wood cellulose fibers, where the individual microfibrils have been partly or totally detached from each other. MFC is normally very thin (˜20 nm) and the length is often between 100 nm to 1 μm.
MFC can be produced in a number of different ways. It is possible to mechanically treat cellulosic fibers so that microfibrils are formed. However, it is very energy consuming method to, for example, shred or refine the fibers and it is therefore not often used.
The production of nanocellulose or microfibrillated cellulose with bacteria is another option. In contrast to the above, this is a bio-synthetic process starting from another raw material than wood fibers. However, it is a very expensive process and time consuming.
It is also possible to produce microfibrils from cellulose by the aid of different chemicals which will break or dissolve the fibers. However, it is difficult to control the length of the formed fibrils and the fibrils are often too short.
One example of production of MFC is described in WO2007091942. In the method described in WO20070912942, the MFC is produced by the aid of refining in combination with addition of an enzyme.
One common problem with the techniques according to prior art is that the process conditions are not favourable for scale-up or large industrial applications requiring high quantities.
Thus, there is a need for an improved process for the production of microfibrillated cellulose.